The basic image-forming process of color photography comprises exposing a silver halide photographic recording material to light, and chemically processing the material to reveal a useable image. The fundamental steps of this processing typically entail: (1) treating the exposed silver halide with a color developer wherein some or all of the silver halide is reduced to metallic silver while an organic dye is formed from the oxidized color developer; and (2) removing the silver metal thus formed and any residual silver halide by the desilvering steps of bleaching, wherein the developed silver is oxidized to silver salts, and fixing, wherein the silver salts are dissolved and removed from the photographic material. The bleaching and fixing steps may be performed sequentially or as a single step, which is discussed herein as blixing. In some methods of color image formation, additional color or black & white development steps, chemical fogging steps and ancillary stopping, washing, accelerating and stabilizing steps may be employed.
In many situations, the useable image is provided to a customer by a multi-stage method which involves exposing a light sensitive originating element to a scene, and developing and desilvering that originating element to form a color image. The originating element may, for example, be a color negative film or a motion picture negative film. The resultant color image is then used to modulate the exposure of a light sensitive display element, with optional enlargement, in a printer. The display element may, for example, be a color paper, an intermediate film, or a motion picture projection film. The exposed display element is then developed and desilvered to form a useful color image which duplicates the original scene.
Originating elements are typically designed to allow good exposure with available light under a wide variety of lighting conditions, that is, good sensitivity (speed/grain) and dynamic range (long latitude and low gamma) are desired. Conversely, display elements are typically designed so as to allow a full range of density formation after well defined exposure and process conditions in a printer, that is, good image discrimination (high density and low fog), low dynamic range (short latitude and high gamma) and easy and consistent processing are desired. These greatly different needs are typically met by providing originating and display elements that differ markedly in silver halide content and composition as well as in the layer orders and types and quantities of image forming chemicals employed in each. One major difference in composition is evidenced in the use of silver iodobromide emulsions in the originating element, a color negative film for example, for their high sensitivity and desirable image structure properties and the use of silver chloride or silver chlorobromide emulsions in the display element, a color paper for example, for their low sensitivity, short latitude and good developability, as well as their ease of reproducible desilvering.
These differences in design needs have resulted in a situation where different developing and desilvering (bleaching and fixing) agents are commercially preferred for each type of film, with the iodide containing originating films typically requiring more potent developing, bleaching and fixing agents. These differing requirements result in both an ecological burden due to the nature of the more potent reagents required and a commercial burden due to the need for a photofinisher, for example to stock and employ a wide variety of process chemicals.
Several approaches to resolving these environmental and commercial difficulties have been reported.
European Patent Application 0,468,780 describes less active developer formulations especially useful with a color negative originating film in which the silver iodobromide emulsions have been replaced by cubic silver chloride emulsions featuring &lt;100&gt; crystallographic faces much like those employed in a color paper. This reference utilizes traditional film desilvering processes.
U.S. Pat. No. 4,952,490 describes a color negative film employing large, optimally sensitized regular shaped silver chloride emulsions featuring &lt;111&gt; crystallographic faces. Organic grain surface stabilizers and sensitizing dyes are added at precipitation to stabilize the grain surface and shape. It is suggested that this color negative film is suitable for simultaneous processing with color paper. Images printed from emulsions containing a large volume of regular shaped silver chloride grains are generally grainy. Normally, high sensitivity is not available because of roll-off in sensitivity of even larger symmetric emulsions due to decreased intralayer light scatter, decreased dye density yield on color development and decreased quantum sensitivity with increased grain surface area.
U.S. Pat. No. 4,952,491 describes a color negative film employing large, optimally sensitized tabular shaped, low aspect ratio, silver chloride emulsions featuring &lt;111&gt; crystallographic faces. Organic grain surface stabilizers and sensitizing dyes are added at precipitation to stabilize the grain surface and shape. With tabular shaped grains, one typically expects to achieve increased sensitivity by increasing the grain surface area without increasing the grain volume, i.e. by increasing the grain aspect ratio. With these emulsions, greater sensitivities resulting from higher aspect ratios are apparently not available because of increased and unacceptable pressure fog reportedly encountered on increasing the aspect ratio.
Japanese Kokai 04-101,135 describes a method for processing a color paper and a color negative film both comprising silver chloride cubic emulsions in common process chemicals so as to enable both rapid and convenient processing. Cubic shaped emulsions appear to be employed in both the color negative film and the color paper and known processing solutions are employed. Such negative films again face the low sensitivity problem previously described.
U.S. Pat. No. 5,104,775 describes a method for processing a silver iodobromide based color negative film and a silver bromochloride based color paper using common bleach-fix and stabilizer-wash solutions. The method minimizes the formation of sensitizing dye stain in the color paper and the color negative film but suffers from poor desilvering of silver iodobromide based films in bleach-fix baths and gives no improvement in process time.
U.S. Pat. No. 5,116,721 describes the rapid processing of silver bromochloride based color papers using the so called "jet-stream" method whereby high surface agitation is obtained. The use of this method for the processing of both an originating film and a display film in common processing solutions is not described.
There remains a need for a method of processing both originating and display photographic elements in substantially the same processing solutions. Such processing solutions must be economical and environmentally sound, without sacrificing the photographic sensitivity and stability of the originating film or the speed and convenience with which these display images can be provided to a customer.